1. Field of the Invention
The present invention relates generally to a navigation system and method, and in particular, to a navigation system using a wireless communication network and a route guidance method thereof.
2. Description of the Related Art
A typical navigation system pinpoints the present position of a moving object on a map displayed on a display based on information received from the GPS (Global Positioning System). The navigation system provides information necessary for driving such as the heading of the moving object, the distance to a destination, the velocity of the moving object, a route set by a driver before departure, and an optimum route to the destination. The navigation system or GPS device is mounted to a moving object such as a vessel, an aircraft, and a vehicle to acquire the position, velocity and route information of the moving object. Particularly, the navigation system calculates the position of a moving object according to signals indicating a 3-D coordinate (latitude, longitude and altitude) position received from GPS satellites and pinpoints the present position to its driver visually or audibly.
FIG. 1 illustrates a typical navigation system configuration. The following description is made in the context of a navigation system-equipped vehicle.
Referring to FIG. 1, a GPS receiver 12 receives signals from a plurality of GPS satellites via an antenna (not shown). A gyro-sensor 14 and a velocity sensor 16 form a sensing unit for sensing the driving angle and velocity of a vehicle. A map data storage 18 stores map data and other additional information. The map data storage 18 is usually a CD-ROM (Compact Disk-Read Only Memory).
A controller 10 provides overall control to the navigation system. For example, the controller 10 calculates the present pseudo-position of the vehicle based on information about the driving angle and velocity of the vehicle received from the sensing unit and selects one of present pseudo-position coordinates received from the GPS receiver 12 and the calculated pseudo-position coordinates. If an accumulation error of the sensing unit is small, the calculated pseudo-position is selected and, if the accumulation error is large, the accumulation error is compensated for with the value received from the GPS receiver 12. Aside from the present vehicle position, the controller 10 calculates the velocity and direction of the vehicle. Based on the traveling information, the controller 10 reads the map data of the neighborhood from the map data storage 18 and displays it on a display 26 while outputting it through a speaker 29. The controller 10 additionally provides an optimum route leading to a destination. A ROM 20 stores an operation program for the controller 10 and a RAM (Random Access Memory) 22 temporarily stores data processed during the operation of the navigation system. A graphic processor 24 processes the traveling information to graphic data for the driver to view The display 26 displays the graphic data. The display 26 can be a CRT (Cathode Ray Tube) or an LCD (Liquid Crystal Display). A voice processor 28 processes the traveling information to voice data for the driver to hear. The speaker 29 outputs the voice data. The graphic processor 24 and the voice processor 28 process map data read from the map data storage 18 and graphic data representing varying states during operation to graphic data and voice data, respectively.
The thus-constituted navigation system is mounted as a separate device to a moving object, like a vehicle, to offer services such as route guidance to its driver. However, this navigation system has limitations in providing route guidance reflecting real-time varying traffic conditions and dynamic road conditions. Meanwhile, real-time varying traffic conditions can be informed via a mobile terminal like a handheld phone without using a separately procured navigation system.
FIG. 2 illustrates a conventional navigation service provided via a mobile terminal, that is, over a wireless communication network.
Referring to FIG. 2, a user can acquire traffic information visually from a display or audibly from a speaker in the mobile terminal. The traffic information, however, represents mere traffic conditions of a particular road rather than guiding the user to a safe and suitable route avoiding congested roads.
Meanwhile, a route guidance scheme can be explored with a navigation system-equipped mobile terminal. The route guidance requires a large capacity memory in the mobile terminal since it depends on a map database. For example, a 30 to 200 MB memory, though the memory requirement varies with digital map databases, is required to build a database with the map data of the overall areas of Korea.
Yet, mounting the large capacity memory to the mobile terminal is against the trend of miniaturization and increases cost. Moreover, use of a fixed memory for a map database, such as a CD-ROM, a flash memory, a mask ROM, or a hard disk, makes it difficult to update the map database adaptively to changes in road conditions or traffic regulations and provide route guidance with real time traffic condition information.